Seems to do a complete reset of things. All my hidden stuff, re-appeared. But before where hiding would take forever, due to searching for updates, now it just takes seconds. After hiding, it did take me bak to the main folders, so I had to reopen the folder again, but it's nothing, and took less than a minute to get things back to how I liked.
Being that it wasn't trying to update, I took a look to see where this was now triggered and saw it in the setting cog icon. There also was a list of 16 things I'd hidden with a check box.
I like how this has been done, makes hiding and keeping things clear much more intuitive.
The more things hidden, the less checked for updates, the faster the checking.
My CCC update also looked to be hanging, and stayed on 0% for a few mins, then when I looked at the screen next, it was dione and updated.